1. Field of the Invention
The present invention relates to determining the level of fluid in a container and the like.
2. Description of the Art Practices
U.S. Pat. No. 5,655,839 issued to Schmidt, et al., Aug. 12, 1997 describes an IR temperature sensor that comprises a sealed housing containing an inert gas atmosphere and enclosing a detector for conversion of heat radiation into an electrical signal, an optical system which images the heat radiation emanating from an object onto the detector, a heat-conducting temperature equalization element which maintains the detector and the optical system at a common temperature, and a temperature sensor which measures the temperature of the temperature equalization element. The sealed housing protects the sensor from the external environment and maintains uniform temperature between the optical system and the sensor.
Further information concerning infrared temperature sensors is found in a brochure entitled Raynger® ST™ that describes ST30 PrO™ Standard and ST30 Pro™ Enhanced noncontact thermometers. The ST30 Pro™ Standard and ST30 Pro™ Enhanced noncontact thermometers are available from Raytek Corporation 1201 Shaffer Road Post Office Box 1820 Santa Cruz, Calif. 95061-1820.
U.S. Pat. No. 4,362,645 that issued to Hof, et al. Dec. 7, 1982 describes temperature-indicating compositions of matter. U.S. Pat. No. 4,362,645, in particular describes stable compositions of matter which change color sharply upon a transition from a liquid state to a solid state or from a solid state to a liquid state, which change of state is at substantially a predetermined temperature corresponding to a temperature to be measured.
The constituents of the Hof, et al. compositions of matter comprise: 1. a solvent (I) consisting of a single substance or a mixture of substances and adapted to change from a solid state at substantially a predetermined temperature to a liquid state and 2. an indicator system (II) consisting of one or more substances different from (I), characterized in that (a) (II) is soluble in (I) when the latter is in the liquid phase, and (b) (II) changes color visible to the naked eye when (I) passes from the solid to the liquid phase or from the liquid to the solid phase. Thermometers containing said stable compositions of matter are also disclosed.
U.S. Pat. No. 4,339,207 also to Hof, et al. which issued Jul. 13, 1982 describes a temperature indicating device is disclosed comprising: (a) a flat or gradually curved heat-conducting carrier having one or more cavities, each substantially filled with a composition of matter; or in the alternative, with (1) a composition of matter which changes from opaque to transparent upon a corresponding change from solid to liquid on top of an (2) indicator means located at the bottom of the cavity; said composition of matter, whether novel or not, being substantially without impurities and containing a substantially spherical void space between the bottom of the cavity; and (b) a transparent cover sheet means in sealing engagement with the heat conducting carrier means overlying and above the cavity, which spherical void space acts to magnify the color change if the novel compositions of matter are present or the presence of an indicator means upon melting of the compositions of matter in the cavity.
The compositions of matter of Hof et al., are further described as changing color sharply upon a transition from a liquid state to a solid state or from a solid state to a liquid state, which change of state is at substantially a predetermined temperature corresponding to a temperature to be measured.
U.S. Pat. No. 4,232,552 issued to Hof, et al. Nov. 11, 1980 discloses temperature-indicating compositions of matter. The Hof, et al. compositions Novel and stable compositions of matter are disclosed which change color sharply upon a transition from a liquid state to a solid state or from a solid state to a liquid state, which change of state is at substantially a predetermined temperature corresponding to a temperature to be measured. The constituents of the novel compositions of matter comprise: 1. a solvent (I) consisting of a single substance or a mixture of substances and adapted to change from a solid state at substantially a predetermined temperature to a liquid state and 2. an indicator system (II) consisting of one or more substances different from (I), characterized in that (a) (II) is soluble in (I) when the latter is in the liquid phase, and (b) (II) changes color visible to the naked eye when (I) passes from the solid to the liquid phase or from the liquid to the solid phase. Thermometers containing stable compositions of matter are also disclosed in U.S. Pat. No. 4,232,552.
Seiden, et al., in U.S. Pat. No. 5,426,593 issued Jun. 20, 1995 is directed to a device which measures the oxygen component of a beverage gas using a specific oxygen probe, ultrasonic degassing, a special valving technique, and microprocessor based software. The measurement is made in the gaseous state in a two-chamber system.
The device of Seiden, et al., is controlled by an electronic console that is built around a microprocessor which sequences and times the valves, receives the data from the oxygen probe and its accompanying temperature compensation circuit, and displays the data. An alternative method is to use several chambers and one pass. Additional chambers may be used to increase the speed of the test, control interferences, or aid in identifying gases other than the oxygen component. The device may also have an interface piercing head manifold that allows carbon dioxide and oxygen to be tested in the same container and in one preparation. The invention also relates to specific gas measurements with non-specific type measurements and the general techniques can be applied to environmental problems that involve oxygen demand and respiration of bacteria.
U.S. Pat. No. 6,119,464 issued to Nakayama, et al. on Sep. 19, 2000 describes beverage servers and controlling methods for beverage servers. More particularly, Nakayama, et al. discloses a beverage server comprising a tank containing water serving as a coolant and a coiled beverage duct through which beer or other beverage flows and cooling means fitted to a portion of the wall of the tank so as to rapidly cool and serve beer or other beverage discharged from the storage container. The inner wall of the tank near the portion where the cooling means is fitted is made of a material having a high thermal conductivity, whereas the inner wall of the tank near the beverage duct is made of a material having a low thermal conductivity. A sensor is provided near the beverage duct to obtain information for controlling the cooling means. This simple beverage server assures stable serving of beverage at a suitable temperature. Another sensor is provided near a portion of the tank wall where the cooling means and a controller to controls the action of the cooling means based on the information from the sensors are also provided. The cooling means works at full capacity when one or both of the sensors have detected the melting of the coolant. This eliminates the risk of trouble due to cooling capacity deficiency even after a long interruption of cooling.
Furuhashi, et al., in U.S. Pat. No. 5,165,569 issued Nov. 24, 1992 recites a keg body for retaining draft beer substantially has adiabatic structure, in which draft beer filled in the keg body is kept cool. A part of the keg body is provided with a face which is not heat-insulated and this face is utilized as a cooling face. In case of necessity, beer is cooled from the outside through the cooling face to keep cool draft beer inside the keg body.
The reader is also directed to Hammerhead Products Accu-Level propane tank gauge. Hammerhead Products is located at 1720-22 Street Santa Monica, Calif. 90404.
To the extent that the foregoing patents are relevant to the present invention they are herein incorporated by reference. Temperatures herein are given in degrees Fahrenheit and pressures are in gauge Kpa. Ratios and ranges may be combined.